Re: True or False?

All differential quantities, whether they be voltage or impedance, etc. are
derived quantities. They come from the node voltages and can always be
defined in terms of the node voltages.

If the current IBIS specs allowed for arithmetic operations, then
diffential quantities could be defined in terms of the node quantities.

ed sayre
--------------------
At 10:49 AM 10/8/98 -0700, you wrote:
>Arpad,
>
>The Spec explicitly does NOT allow either side of the series device to
>be anything except terminator. So how can you have a differential
>relationship (such as vdiff, or tdelay) between terminators (there's
>no sensing nor driving)? I argue that if that component is not
>sensing the voltage difference on those pins then from the point of
>view of that component, the pins are not differential.
>
>Note that if you want the nets to be connected differentionally, this
>would occur at a another component(s) on the board which would have an
>actual differential driver or receiver pair triggering an electrical
>association between the nets.
>
> I+ ---series--- O+
>
> I- ---series--- O-
>
>Would it be sufficient to define the [Series mapping] only and not the
>[Diff Pin] relationship for the above case?
>
>Chris
>
>>
>>
>> I would vote for FALSE, because I could see them being used together in a
>> situation where you have a differential pair going into the chip and come
>> out on
>> two other pins though a series model. For example, let's make
>>
>> pin2 = diff_in+
>> pin3 = diff_in-
>> pin4 = diff_out+
>> pin5 = diff_out-
>>
>> where the ins and outs are "shorted" with metal.
>>
>> In this case the [Diff Pin] keyword would associate pins 2-3 and pins
4-5 as
>>
>> differencial, but the [Series Pin Mapping] keyword would connect pins 2-4
>> and
>> pins 3-5. Since the series models ignore the C_comp, the only way I can
>> enter
>> the die capacitance into this picture is if I use the Terminator model on
>> each
>> pin with nothing but C_comp in it.
>>
>> This is how I can see the series and terminator models used together with
>> differencial pins.
>>
>> Arpad
>> ==========================================================================
>>
>
>

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Received on Thu Oct 8 11:45:47 1998